The present invention provides a fluid composition for use in a shock absorber, which has high abrasion resistance and a low coefficient of friction, and a shock absorber containing said fluid composition.
Hydraulic shock absorbers utilize a hydraulic fluid to absorb shock. Such shock absorbers include car shock absorbers which dampen the objectionable spring oscillations to provide a smooth ride of a car, hydraulic shock absorbers to lessen shocks in landing of aircraft, door checkers, etc.
The primary characteristics required for a shock absorber fluid, particularly a shock absorber fluid for a vehicular shock absorber follow:
(i) High abrasion resistance (durability); PA1 (ii) Low coefficient of friction (comfortable running); PA1 (iii) Does not attack and deteriorate the shock absorber seal (prevention of liquid leakage). PA1 (a) a lubricating base oil; PA1 (b) 10 to 1,000 ppm (by weight), calculated as boron, of a boron-containing compound; and PA1 (c) 100 to 3,000 ppm (by weight), calculated as phosphorus, of a phosphoric acid ester and/or a phosphorous acid ester.
High pressure agents and lubrication agents have been widely used to provide high abrasion resistance and a low coefficient of friction. When using such high pressure agents and lubricating agents in a shock absorber in which there are various types of friction, such friction between a rod and a guide, friction between a rod and a seal, and friction between a piston and a cylinder, satisfactory results are not obtained since many of such agents exert adverse effects on the seal and they cannot be used satisfactorily over a wide temperature range.